How can I get my motor to go without major mods?
Modifying motors has been every model boaters secret ever since I started boating in 1981. In fact even when my father started boating in 1972 there were various secrets about what you do and what works. Well this article is about to reveal some secrets that I think are no longer secrets to many people that have been involved but could really help those new comers in the game.
It must be noted that the mods I am going to tell you are mods that have worked for me and in many cases are still working for me. If you want to do these mods you are also going to do them at your own expense and risk. I would advise you to get more detail before you actually attempt to do these mods, as I will only be giving a brief description of the mods.
The first thing I always do when I buy a new motor is strip it down completely. There are various Mods that can be done on the timing of the sleeve but I am not going to talk about that now. You can refer to Prestwich Models in the UK for more details on that. Before I start to re-assemble the motor I take all the sharp edges off the casing and sleeve as a result of machining.
MOD 1:
Take the engine casing and look into the back of the motor where the crank normally would have been. You will see that the crank case has been machined nicely round to allow the crank to rotate. But on each side where the side inlet port starts, there is a little lump of metal still left due to the way the machining is done. That metal is machined away to make it a smooth straight flow up from the crank case to into the inlet side port. Do not polish the ports inside as it is better to leave it with a rough-like surface. See picture.
MOD 2
Your cylinder head gap is normally set from the factory for a specific Nitro mix and normally the motor manufacturer informs you of the recommended fuel to be used. Take note that when you use more Nitro than recommended you need to reduce the compression ratio and or make your glow plug colder. If you run above sea level you need to increase the compression ratio. The exact gap would be impossible to tell you as each motor would vary depending on the head, altitude, plug and fuel mixtures. But this is an area that is very critical. How do I know if I am too High or too Low? That is the important answer to know. If you have a Too High compression ratio you will be blowing plugs. But then again if you have a too hot plug and lean mixture you can blow plugs as well so that does not help you, you may say. Yes, that`s true, but if you have set your motor that the mixture is a little on the rich side and you have already put in the recommended cold plug, and it still blows, then you have an idea that the ratio is too high. A better indication would be if you see small pit marks on the head if you remove it. That would be a sign of pre-ignition. Action: Colder plug, reduce your compression ratio or reduce your Nitro mix. I think I have said enough about that Mod.
MOD 3
The piston is cut away by the centre inlet port to allow for better flow. Most new engines already do this and thus you need not increase that cut away much more. However, I have seen some pistons that are almost not recognizable due to the cutting away. Take note that on the smaller motors you should not cut too much away as the piston requires the length to prevent it from twisting. It must be noted that better flow is not the only reason for cutting it. You may be getting more revs due to the weight reduction as well.
MOD 4
On the casing once again, I always increase the exhaust outlet port with the grinder. During this process, I remove any lumps, and then shape it to allow a smooth flow. Even polish it if you can.
General:
There are various mods that are done on the inlet port timing and will not be able to tell them to you as they are more advanced type of mods together with the sleeve mods. In addition each motor type has its unique requirements depending on the inlet arrangement. Most motors that you buy are already in the best all round performance position and need not be tampered with. If the above alterations are done to your motor you should have a motor that works well!
. -ENJOY !!
Compiled in September 1997 by Gary Baldwin
Last Updated on 29 December 1998
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